Overload tripping switch



E. J. HAGDAHL OVERLOAD TR'IPPING SWITCH Dec. 17, 1957 8 Sheets-Sheet 1Filed Deo. 22. 1954 Dec. 17, 1957 E. J. HAGDAHL OVERLOAD TRIPPING SWITCH8 Sheets-Sheet 2 Filed DeG. 22. 1954 L y MJ @E wim Mg M M f Dec. 17,1957 E. J. HAGDAHL OVERLOAD TRIPPING SWITCH Filed Dec. 22. 1954 8Sheets-Sheet 5 Dec. 17, 1957 E, J, HAGDAHL 2,816,986

OVERLOAD TRIPPING SWITCH Filed DBG. 22. 1954 8 Sheets-Sheet 4 IN VEA/rw?ERA/Jv' fof/9N Hasn/wa 5f mi@ Dec. 17, 1957 E. J. HAGDAHL ovERLoADTRIPPING SWITCH 8 Sheets-Sheet 5 Filed Dec. 22. 1954 3f @mi Hw /Qrro RNEr Dec. 17, 1957 E. J. HAGDAHL 2,816,986

ovERLoAD TRIPPING SWITCH Filed Dec. 22. 1954 8 Sheets-Sheet 6.

/Qrromvfr Dec. 17, 1957 E. J. HAGDAHL ovERLoAD TRIPPING SWITCH 8Sheets-Sheet 7 Filed Dec. 22. 1954 rro mvfr Dec. 17, 1957 E. J. HAGDAHL2,815,986

OVERLOAD TRIPPING SWITCH Filed Dec. 22, 1954 8 Sheets-Sheet 8 ArfoR/vfrUnited States Patent O ovERLoAD TRrPPlNG SWITCH Johan Hagdahl, Bromma,Sweden, assignor to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden,a corporation of Sweden Application December 22, 1954, Serial No.476,954 Claims priority, application Sweden December 23, 1953 Claims.(Cl. 200-116) The invention relates to an overload tripping switch ofthe type in which the operating system comprises a knee-joint mechanismwhose motion can be controlled either by a manually adjusted, operatingmember or by the motion of a member, sensitive to the action of heat, e.g. a bimetallic strip. Such switches have the disadvantage that theswitch, if it is in on position, opens due to jars or causes momentaryinterruptions in the circui-t that the switch controls. Switches of thistype which are known up to now have also a complicated design. Thepresent invention intends to provide a switch of this type, in which thenow mentioned disadvantages have been eliminated.

The invention will be further described with reference to the attacheddrawings which show a number 4of ernbodiments.

Fig. 1 shows on a large scale a switch viewed from the side with oneside plate removed. Fig. 1 A-C shows the link mechanism shown in Fig. 1in diierent positions. Fig. 1 D shows a part of the operating device inanother position than that shown in Fig. 1.

Figs. 2, 4 and 10 correspond to Fig. 1 but are made on a reduced scalein which case the parts, however, shown in Figs. 4 and 10 are shown inthe position they have when the switch is in o position. Fig. 4a is asection taken along the line E--E in Fig. 4. Figs. 3, 5, 6 and 7 aresections taken along the lines A-A, F-F, G-G and D-D respectively inFig. 2.

Fig. 8 is a side view of the switch with mounted side plate.

Fig. 9 is an enlarged elevational View of the movable and iixedcontacts.

Fig. 11 shows, viewed from the front, three switches which form a unit.Fig. 11a shows a detail.

Fig. 12 is a section taken along the line H-H in Fig. 2 whereby it isassumed, however, that three switches are placed side by side.

Fig. 13, A, B and C, show a blocking arm Viewed from the side and thetop respectively.

Fig. 14 A and B show a link viewed from the front and the siderespectively.

Fig. 15 A and B show a connecting arm viewed from the side and the toprespectively.

Figs. 16-19 show a modication whereby Figs. 16-18 show, viewed from theside in ydiiferent positions, the parts of the mechanism according toFig. 1 which are affected by the modification. Fig. 19 shows a sectiontaken along the line I--I in Fig. 16.

All components of the switch are mounted between two side plates 11 and11a, of which 11 in one edge is bent to form an L-member 22. Theturnable parts of the switch are carried by journals with bearings inthe two side plates 11 and 11a. In Fig. l is shown the position of thevarious components when the switch is in on position. The circuit forthe current that is to be switched oi is connected to the terminals 1and 7 and the current passes from the terminal 1 through a bimetal 2 andthe CFI ICC

terminal 5 and through the contact arm 6 operated by the switch which ispivoted at its right end, the contact arm 6 (Figs. 1, 3 and 7) which isU-shaped in section being on either side provided with a tab 23 whichrests in a slot 72 in 4a plate 71 of insulating material arranged on theinside of each side plate 11 and 11a respectively. Said slot 72 (Fig. l)has a sloping edge at the top whereby the arm 6 is allowed to take theposition shown by lines `of dots and dashes in Fig. 1. The arm 6 is inits ends provided with contact members 6a and 6b which can be heldagainst the fixed contact terminals 7 and 5.

The operating members of the switch consist of a rocker arm 8, 25,whereby 8 is the handle and 25 the lower part of the arm comprising twopieces of plate of the same shape which are parallel with each other.The rocker arm is pivoted on a journal 10, fastened between the sideplates 11. In the part 25 there is a slot 12, in which the journal 13rests on which is pivoted one end of a connecting arm 14, whose otherend is connected by a journal 27 with a knee-joint mechanism. Thismechanism comprises two links 17 and 18 connected with each other bymeans of the journal 27 and a releasing arm 20, connected with the link18 by means of a journal 29. The journal 13 is held in its position bythe two Shanks lof a shear spring 15 (Fig. l) which is placed around thejournal 10 and whose shanks rest against 'a pillar 16 fastened to therocker arm member 25. A spring 19, placed around the journal 10 andresting against the journal 13, tends to turn the rocker arm in thedirection ot the arrow 9. If the switch is in the off position (Fig. 4)the last mentioned turning tendency will result in that the left shankof the shear spring 1S pushes the journal 13 with the connecting arm 14and the journal 27 to the right, which results in a pull in the links 11and 18. Thereby the free end of the link 17 tends, via the journal 39,to turn the contact arm 6, journalled in the tabs 23, against a xed shoe19 and the free end ot' the link 18 tends-by action of the journal 29which is journalled in the releasing arm 2t) and which in this positionrests against the upper edge of a slot 28, arranged in the link 18--toturn the releasing arm 20 counter-clockwise around the journal 24, onwhich it is journalled in the side plate, so that the tree end 21 ofthis arm rests against the gable piece 22. Hereby the components or' theswitch have the position shown in Fig. 4 and the connection between thecontacts 6a and b and the xed contacts 5 and 7 is broken. The arm 6 mayhave only one switching-ott point 6a, 7 and the contact members 6b and 5may be omitted. `When the switch is operated in the on position, theparts should be changed from the position shown in Fig. 4 to theposition shown in Fig. 2 and the handle 8 is thereby turned clockwise(Fig. 4). The spring 19 is hereby tensioned and the connecting arm 14with the journal 27 and the links 17, 18 is brought to the left throughthe pressure which is exercised by the right shank of the shear spring15 against the journal 13. A coil spring 30 whose free ends rest againstthe journals 27, 29 tends to press the journals in the direction awayfrom each other. When the journal 27, inuenced by the .connecting arm14, is moved to the left (in Fig. 4), the knee, formed by the links 17and 18, will be straightened out which involves, partly that the link 17turns the connecting arm 6 around its bearing 23 at the right end of thearm, so that its left contact 6a moves towards the fixed contact 7, andpartly tha-t the pull from the link 18 upon the journal 29 ceases,through which `the spring 34 (see also Fig. l), which has its one endpressed against the L arm 22 and its other end brought through a hole62a in the releasing arm 20, can turn the connecting arm 20 clockwiseuntil the free end 21 of the arm 20 strikes against a shoe 51 on ablocking arm 36 (Figs. 1, 5 and 13).

As mentioned above, the link 18 is made with two equal link halves whichare parallel with each other, each being provided with a tab 31 (Figs.1, 3 andY 8), which projects at right angles to the side plate 11, andis brought through a slot '70'in the side plate (Fig. 8). The lower edge32 of the slot 70 forms a guiding surface for the tab 31, said guidingsurface being provided with a notch 38. For the sake of simplicity onlythe edge 32 and the notch 38 of the slot 78 have been drawn in Figs. 1,2, 4, 9 and 10. When the link 18 moves horizontally the tab 31 slidesagainst the guiding surface andv when the tab reaches the notch 38 itcan drop down into the same which permits a displacement of the link 18in a downwardly direction, which will be further described, inthefollowing. When the switch isV inthe of position the tabs 31 hastheposition shown in Fig. 4 and. thevposition shown by dotted lines 31a inFig. 1 and, when switching on, each tab 31 moves down and strikesagainst the guidf ing surface 32 and slides thereafter along thehorizontal edge of the guiding surface. Duringthe lastmentioned motionthe left end 6a of the contact arm 6`takes aposition between the shoe 19and the Xed contact 7. At the same time the spring 30 is ltensioned andtheA arnrlS with the slot 28 is brought upwards relative to the journal29. The pull force in the arm 14-which is necessary to tension thespring 30 and to overcome the friction between the tabs 31` and theguiding surface 32, when the rocker arm 8, has been turned clockwiseduring the motionloads the shear spring 15 until the journal 13 restsagainst the right edge` of the slot 12. Close to the final position ofthe rocker arm the tab 31 has been brought forward to thecorner 37 onthe action of guiding surface 32 (Fig, 1A) and by the shear spring15-which presses against the journal 13 and brings this back to itsvrest position in the middle of the slot 12 between the shanks of the.shear spring 15, when the friction betweenthe tabs 31n andthe guidingsurface 32 decreases-the tab 31 is drawn over the corner (Fig. 1B),after which the tab 31 on account of the pressure from the spring isquickly brought down into the notch 38 of the guiding slot. As a result,the contact arm 6 is quickly brought down against ythecontact members 5and 7 through which a momentary closing of the current circuit isobtained. Necessary Contact pressure is obtained by the pressure fromthe spring 30,A

whose whole pressure is taken up, partly by the journal 29 andpartly--bymeans of the journal27 and the Varm. 17-by the contact arm 6. The twohalves of ,theglink 18 (Figs). 3 and 14) are kept together by amiddle'piece 18a and that part of the releasing arm Ztl, which islocated between the journals 24 and 29, also consists of two platemembers, connected with each other, and kept together by avmiddle piece43. Also the'link 17 'consists of two equal pieces which are parallel toeach other (Fig. 3) suitably of. insulating material in order toinsulate the contact armfrom the mechanism. FromFigs. 1 and 14 itisclear that near the/middle piece 18e on the link' 18 is bent andfastened, e. g. by'a rivet 7S, aleaf spring 44 whose upperend.44a.projects slightly over themiddle piece 18e and co-operates withthe middle piece-43 on the arm Ztl `in such a way that when the switchis in on position (Fig. 1) the upper edge of the-end 44a is only arelatively short distancel from the lower edge of the iniddle member 43,through which it is prevented that the links 17 and 18, when theswitchis subjected to jars, move any appreciable distancein their lengthwisedirection (upwards in Fig.l l). The leaf spring-44 has at the top Va tab44h (Figs.,1 and 14) which prevents the spring metre between the upperedge of the springend 44a andA t the middle piece 43 when the switch is011, which implies that the links 17 and 18 can only move 0.2millimetreV in the lengthwise direction. Thereby it is prevented thatthe switch releases for shakes since it is required for making areleasing by a jar possible, that the link 18 moves upwards (in Fig. 1)so much that each of the tabs 31, which is carried by the same, is movedout of the notch 38. From the drawing (Fig. l4b) it is clear that thespring 44 is rmly fastened` to the middle piece 18C in` such a way thatthere is a certain space a between the spring and the inner surface ofthe middle piece through which the spring can be bent when it pressesagainst the middle piece. This means that when the link system istransferred from released to closed position (Fig. 1A) and cach of thetabs 31 during their motion in the slot 32 is at the edge 37 of thenotch 38, the spring end 44 strikes against the corner of the middlepiece 43 and is bent against the middle piece 18o in order then, whenthe tabs sink down into the notch 38, to slip over the edge of themiddle piece 43 and take the position shown in Fig. 1.

On the other hand, when the switch releases, the link 18is turnedrelative to the arm 20 and the spring 44 is thereby brought to such aposition that it cannot block the link 18 (see Fig. 4).

The spring 44 now described, in combinationwith a spring 41 in thecontact arm 6 (see Figs. 1, 2 and 3), also prevents that the contactbetween the contact members 6a, 7 and 6b, S respectively is momentarilybroken by jars, that is, blinkings are prevented. Said spring 41, whichconsists of a leaf spring, is placed in the bottom of the arm 6 which isU-shaped in section and provided` with a cavity on the middle, in such away that the ends of the spring rest against the bottom of the arm 6 butthe center section is at a certain distance from same bottom. Thejournal 39 (Fig. l), whichis journalled in the link 17, passes throughan oval-shaped hole 40 in the'arm 6. When the Contact between the arm 6and the contact 7 is broken, as shown in Fig. 1A, the spring 41 pressesthe journal 39 against the upper edge of the hole 40, but when theswitch is on (Fig. 1) thelink 17 will, on account of the springlpressure from the spring 30, be pressed downwards, whereby the journal39 is pressed down against the lower edge of the hole 40 by which thespring 41 is tensioned and the arm 6 is pressed against the contact 7.Even in closed position (Fig. 1) there is a certain space between thelower surface of the spring 41 ,and `the bottom of the contact arm 6 andthe spring 41 tends to press the journal 39 upwards. above, thespring 44on the link 18` allowed that the links 17 and 18 could be displaced byjars about 0.2 millimetre in their lengthwise directions. The playin thehole 40 (Fig. 1) for the journal 39 is greater than 0.2 millimetre and amotion of about 0.2 millimetre in the lengthwise direction of the links17 and 18 will not cause the jour, nal 39 to strike against the upperedge;of the -slot 40 and will therefore not involve that the contact arm6 is lifted, from the fixed contacts 5 and 7. The arm.6.will insteadA17, 18 with the tabs 31 have been displacedupwards and the leaf spring44 has struck against the `shoe surface 43a of the middle piece. Thejournal*l 39 has beenbrought up into the slot 40andthe pressure fromtheleaf spring,i 41, which has relaxed somewhat, is suicient vto press,theV

arm 6 against the fixed contacts 5 and 7.

The leaf spring 41 may be replaced by a coil spring As mentioned.

41h, e. g. a piano wire wound around the journal 39 and withits endsresting againstthe bottomof the arm 6, as shown in Fig. 9.

For a manual releasing of the switch the parts shown in Figs. 1 and 2should be changed to the position shown in Fig. 4 and the rocker arm 8is thereby turned counterclockwise around the journal 10. During theturning the slot 12 will be displaced over the journal 13 and in linalposition the journal will be in the left half of the slot 12. At thesame time the left shank of the shear spring 15 has been loaded andltends to move the journal 13 and the arm 14 (which carries thejournal13) to the right. The arm 14 is mechanically connected with the links17, 18 through the journal 27 and as long as the tabs 31 are in theirnotches 38 the pressure from the arm 14 cannot overcome the knee formedby the links 17, 18 which is the condition for releasing the switch. Toenable this there is an operating arm 46 journalled around a pin 45 inthe rocker arm 8, 25, the appearance of said arm 46 being evident fromFigs. 1 and 15 and which co-operates with the shoe 51 on theabove-mentioned blocking arm 36, the latter one being pivoted around thepin 55, fastened to the bottom plate 11. A spring 52 is wound around thepin 55 and its one shank presses against a pillar 54 in the bottom plate11 and its other shank is at its end 52a perpendicularly bent andpresses against the upwardly directed part 36a of the blocking arm 36 bywhich this latter is given a counter-clockwise turning moment. Themotion is limited by a rm stop member 56. The abovementioned operatingarm 46 is in its free end formed into a hook 50 and is on its lower partformed into a cam 48 which, when the arm 46 is displaced by themovements of the rocker arm 18, 25, slides against a pillar 49 fastenedto the bottom plate, whereby the hook 50 is brought upwards ordownwards. The cam 48 on the operating arm 46 is kept pressed againstthe pillar 49 through the spring 47 placed around the rm pillar 54. Whenthe arm 46, on releasing the switch by the rocker arm 8, is moved to theleft (Fig. 1) the hook 50 strikes against the shoe 51 (see also Fig. 5)and drives this so that the blocking arm 36 is turned counter-clockwiseagainst the action of the spring 52. As mentioned before, the end 21 ofthe releasing arm 20 rests under spring pressure partly from the spring30, which presses against the pin 29, journalled in the arm 20, therebygiving the arm 20 a clockwise turning moment, and partly from the spring34 against the shoe 51 and when this latter one is by the hook 50 movedclear of the end 21 so that this end is no longer restrained by the shoe51, the releasing arm 20 will turn clockwise, whereby the knee, formedby the arm 20 and the link 18, is bent to the left at a somewhat smallerangle than in Fig. 4. The pin 29, which is journalled in the releasingarm 20, is brought up against the upper edge of the slot 28 through thepressure from the spring 30 and during the continued motion, when thespring 34 alone turns the arm 20 clockwise, the pin 29 will carry withit the link 18 whereby the tabs 31 are pulled up from their notches 38.At this moment, when the parts of the mechanism take the position shownin Fig. lc, the pressure from the arm 14 lcan be released and the pin 27with the links 17 and 18 be rapidly carried to the right, whereby thelink 17 pulls up the contact arm 6 so that switching-olf is made and thelink 18-by having the upper edge of the slot 28 resting against the pin29--pulls the pin 29 downwards to the right, giving a counter-clockwiseturning moment, which is greater than and counter to the moment from thespring 30, on the arm 20, so that the end of said arm, previously.turned downwards, is carried upwards until it strikes against theL-member 22 of the bottom plate. All components of the switch have thenbeen changed to the positions shown in Fig. 4. The hook 50 of theoperating arm 46 has thereby-through co-operation between the ca m 48and the pillar 49--been carried upwards to enable that the'blocking armv3.6 with the shoe 51 operated `by 6.. the spring 52 through a clockwiseturning motion can be brought back to the position shown in Fig. 1.

The releasing of the switch can also be made thermally. For this purposethere is a bimetallic spring 2 (Fig. 4a), mounted on the terminals 1 and5, through which spring the current passes and which is heated by thecurrent. On the blocking arm 36 there is by the rivet 74 fastened aband-shaped arm 70 whose end is formed into a bushing 71, in which ascrew 72 is threaded which carries a ball 53 of insulating material. Thedistance between the ball 53 and the bimetallic spring 2 can be adjustedby means of the screw. 72. If it is assumed that the switch is on andthe current exceeds a previously determined value, it is assumed thatthe blocking arm 36-through inuence by the bimetallic spring 2 which bythe heating has turned to the right-has turned counter-clockwise so muchthat the shoe 51 on the blocking arm has been carried away from the end21 by which the releasing arm 20 rests against the shoe -51 and the arm20 can therefore be` turned clockwise and the parts thereby be returnedin the abovementioned manner to the position shown in Fig. 4 under theinfluence of the spring 19 in the rocker arm which spring, when theswitch is ott (Fig. l), tends to carry the arm 14 and therewith the kneebetween the links 17 and 18 to the right.

In the case that the rocker arm 8, after switching on, is retained inits position (as indicated in Fig. l0) and a switching off, caused in athermal way occurs, the releasing arm 20 is under the influence of thespring 34 turned a greater angle than at a normal release. The pin 29 inone end of the releasing arm 20 will thereby bring with it the links 17and 18 and also the contact arm 6 upwards, by which the contact betweenthe arm 6 and the fixed contact 7 even in this case is broken.

A single-pole switch has been described above. In the case that amulti-pole switch is used, e. g. in three sections, it is desirable thatall sections are released even if only one of the sections isoverloaded. This requirement can be fulfilled by building togetherseveral switches according to the invention in a manner that will now befurther explained.

In Figs. ll and 12 is shown a three-pole switch, built together of threesingle-pole switches A, B and C, whereby only the middle switch has beenprovided with a handle 8. When switching on manually the handle 8 on therocker arm of the switch B is operated and to enable thereby that alsothe switches A and C are switched on, 1

the rocker arm of the switch B is provided with driving members which atthe motion of the rocker arm in switch B bring with them the rocker armsin the switches A and C. The lower part of each rocker arm consists, asmentioned before, of two plate pieces 25 which are parallel to eachother (see Fig. l2, which is a section along the line H-H in Fig. 2).Each plate piece 25 of the switch B is now provided with a tab 57 whichis bent up perpendicular to the plate (see Fig. 1 and Fig. 12). Theplate i piece 25 on each side switch A and C respectively, which islocated close to the switch B, is also provided with a tab 56 (Figs. lcand l2), so placed that when the rocker arm in the middle switch B isturned when switching in, the rocker arms in the switches A and C arebrought with it so that even these switches are switched in. The tabs 56and 57 project out of the sides of the side plates 11 and 11a throughopenings 73 made in the same (see Fig. 8).

When switching off-manually or thermally-one of the switches, themotion-transmission to adjacent switch must be made via the blocking arm36, as this arm controls the releasing of the switch. For this purposethe blocking arms 36 in the various switches A, B, C are connectedtogether with one another by connecting arms 58 (see Fig. 1l, details inFig. 11a), which are perpendicularly bent out in the ends. Each blockingarm 36 is provided with two slots 60 (see Figs. 1, 1l, 13A and C).

The connecting arm 58 is riveted with the rivet 59 (see Fig:A 11)to'ithei blocking:VA arrrr36-l of 'thez-'switchgAz and 1 has its leftend.insertedffinvtherleft'slotfll'inzzthe .sarnea blocking-:arma:The=right end ofztherarm1=58lis'inserted in .theleftl slot r60'fintheeblockingfarmscof the switch;

Fig. 11.: The right. (resp.l left) end; of:the.connecting.

arrrrz. 58- (resp; 58a) lis consequently insettedsiinto.- its.'vcorresponding-slot 60mthe blocking 'arrrril of the middle L.

switch B; whereby there eis a1certairr-.space :611.(Figr: 11) betweenthe'connecting arrnz.'58'l(resp;;58.) `andthe upper (resp: lower) edge:of-the. .slot:60,=.which ,enables thatuone blockingv arm 36a of.'thefswitches'aA; B or.-G.respectively,` can :.turn gazzcertainrangle-.without the :connecting i zarmfSS; andcSStz respectivelytouching: any of .ther-sides inx the corresponding .slot60,. thatiscwithoutzthe-arnr 5S, 58a. driving the :blocking zar-m.36-.ofjthe1adjacent switch.; The f force .obtained .from.;the:bimetall2.on .thermal releasing.

is not .sucient i to. turn.-a1l. three @blocking arms. in.. the switchesA, B and C, and the device-has therefore been f so designed thatacertainfadditional. motion-is obtained when one of the switcheshasstarted'tonreleaseg which additional.- motion causes thataalso thetwoi other 'switches rele-ase. On. the releasingarm 20-ineachswitchthere is for this purpose a downwardly directed projection.

part 62, whichican strike against a .pinL 63 onf the blocking arm 36(Figs. 1, 2 and 5).l If the switchfroma closed.

position-(Fig. 2) starts to releaseowing toth'at the bimetal 2 bends andacts upon the insulating ball 53, the blocking arm 36 is. turned Ainthe. manner previously indicated, sothat the releasing arm 20 ismadevfree and turns clockwise,.whereby` the projection part 62 strikesagainst the pin 63A on the blockingk arm 36. The Vclockwise turningmoment of the releasing .arm 20 is effected by the springs 30, 34 and 41and hereby theblocking arm 36 receives an essential. contribution .tothe counter-clockwise turning motion .that is given the armen account ofinuence from the .bimetalf2, .which contribution. issufticient .that theblocking arm 36 of the switchthat has released, e. g. the

middle switch B, shallon its .turningby meansofthe l connecting arms 58and 58a-be able to drive the blocking arms 36 ofthe switches A and C.The space 61 between the connecting arm 58 andthe inner edge of the slot60 vshould be so dimensioned that the end of the arm 5S does not makecontact with the edge of the slot the pin 63 in the last-mentionedswitch, the connecting arrn'58a'will carry with it the blocking arm 36in the switch C whereby all three switches will be released. Inthecasethat by two-pole switching only'two'switches are used, only oneconnecting arm 58 will of coursebe required; The yabove-mentionedadditional motion of the blocking arm 36, which is effected throughco-*operation between the projection part 62 on the arm 20 and the pin63 on the blocking arm 36 ceases'after the tip of the projection part 62has turned the blocking arm4 to such a position that the right edge 64of the projection part 62 slides against the surface of the pin 63. Thelast-mentioned edge is namely formed as a partof a circle,- wh'osecentre is the centre of the journal 24(see Fig;` l).

The-now described additional motion of the'blockingarnr36 has beendescribed in connection with '.thermalre# leasing, but this frnotionwill also take-*place at manual releasing of theswitch, whereby it mayb'e-'assumed'that theihandle 8 ofthe three-polefswitch shown inFig. 1lis operated The -hookfSO` on thearm46Lcarries-=with CII it as:.described ;above,. thezshove 51.v orrithe .blocking .arm

36 .'.when the handler18.. onlrnanual.. releasingfr is turned: However,at the same .timethefarmn counter-clockwise. 46:with:,th'e.shoe 50islifted'KFig-,f 1), on; account ofxcof operation; between. the fcarnn48on` the arm 46s andzth'ei pillarv 49,-.and in the movementwhen.the 'ho0k150 hasl turned .thevblocking arm 36W/,ith the shoe 51 to suchaposition; that'the end 21 of the .releasing arm. 20 .moves clearof-'the-.shoe51,' so.that` the' arm 20can release, the. hook S0'has beenraised so much that, onxthecontinued.

motion to the left of the-arm 146,l it can no longer carry witlrittheshoe 51. releasing `arm'20 strikes :against-the pin'63 on; the.blockingwarrn 36,-forfwhichv reasonveven: in this case an additional..motion -forthe bloc-kinggarm. 36v is obtainedwhich is suficient'toturn:the blocking arm ofthe adjacent switch.

The invention cantbe'modied in .several ways rwithin the scope. of theidea of. thelinvention. the link 18 may be effected, instead of 4by theleaf spring 44, by a spring actuatedblocking member 80, journalled on.the pin 29 (Figstl6.-l9). The blocking member 80 is in its oneendprovided with a shoe Si, intended to cooperate with the pin..27, and inthe ,other endy provided .with a..ilange 82,. against whichV cneend,rests of a coil spring 83, wound around the pin 29, which. spring tendsto. turn the,blocking.mernber tlceunter-clockwise, so that the.ilange82. rests againsty the middle piece 43. in the arm. 20. Whentheswitch. is,.on. (Fig. l) the parts takethe position. shownl in Figs.v16 and19, the shoe 81 is ata slight. distance .from .the pin 27 andfadisplacement ofthe liiik'.1S.iri. its lengthwise direction is thenprevented? by the, blocking.. member 80 since. this is journalledon thepin .29,whichis liked in this position of the mechanism. When the switchis. to be released the arm 20a1idfthe link 18 areturned-as describedaboverelative to eachother and thewarm 20 drives the'blocking member80`to .the position showny in Fig'. l7,`,in which the blockingarm 80cannot prevent. the motion of'the link 18. position the. pin 29 is-justbefore the tabs 31 fallinto the notches 38'-in. the lower part of theslot 28' and on turningrthe link lclockwise aroundthe pin 29, the pin 27engages theshoe Slfand turns away the blocking member 80' clockwise,against the vaction ofthe.spring 83, fromthe position this has when thespring 83 presses the flange 82"against the middle-piece 43 (aboutl theposition the member 80 has in Fig. 16) vand to the position shown inFig. 1S. Fromlthis position the tabs 31 fall down intothe notches lErinthe way described above, whereby theblocking member 841" bythe spring 83is turned counter-'clockwisetothe blocking 'position shown in Fig. 16.vAs `it wouldseem; even in vthis embodiment the blocking member preventsthelink 18 to be displaced in "its lengthwise'direction 'more than alimited part when the'switch ison; withoutfthe blockingrrnemberpreventingthe 'motion;of"thefparts at-on and off operationof'theswitch';

The invention'can also be'modied in such a way that thebandeshaped-'arm' '70, carriedv by the blocking arm 36',lwhich'carries'the Vinsulatingball 53 consists of a bi# metallicstrip,whereby temperature compensation is obtained for tcmperaturevariationsin theambient air. If e. g. the-temperatureV of 'theambient airincreases, it is assumed thatthe bimetallic strip 2 turns to the righton account of vwhich the distance between the strip 2 and the ball hasdecreased-irr the f caseethat the arm 70 consists ofl ordinarymetal-without-any current passing the bimetal. When the'bimetal' 2 isthenheated by the To compensatethis error the'arm70 consists of bimetalso-arranged that when the temperature 'of the air increases.alsothefarmf70 bends -toftherighn vby which thedistance.

At this moment the tab 62 on the.

The blocking of.

When the switch is to beoperated to on' 9 between the bimetal 2 and theball 53 will be the same as before the heating.

I claim:

1. An overload tripping switch having a housing and a knee jointmechanism comprising a first link and a second link, a journal pivotallyconnecting one end of said first link to one end of said second link, aconnecting arm having one end in engagement with said journal foreffecting movement thereof, a movable contact member secured to theopposite end of said first link adapted to engage at least one fixedcontact member, a releasing arm pivotally secured to said housing andbeing pivotally and displaceably connected at one extremity to theopposite end of said second link, a heat sensitive member controllingthe pivotal movement of said releasing arm to a releasing position,blocking means comprising a spring actuated blocking member and ashoulder member, one of said members being associated with said secondlink and the other of said members being associated with said releasingarm, relative rotation of said releasing arm and said second linktowards an engaged position of said movable contact member with saidfixed contact member being operative to dispose said spring actuatedblocking member in blocking longitudinal alignment with said shouldermember, said blocking means limiting relative longitudinal movement ofsaid second link and said releasing arm towards each other when saidmovable contact member is in engaged position with said fixed contactmember.

2. An overload tripping switch as set forth in claim 1, wherein saidblocking member is secured to said second link, and said shoulder memberis fastened to said releasing arm, said blocking member comprising aleaf spring having one end secured to said second link with the plane ofsaid leaf spring at substantially right angles to the plane of saidsecond link, the lengthwise direction of said leaf spring coincidingwith the lengthwise direction of said second link.

3. An overload tripping switch as set forth in claim 2, wherein saidsecond link and said releasing arm each comprise a pair of spacedparallel members, a middle piece connecting each pair of membersintermediate their longitudinal extremities, said middle piece of saidsecond link comprising said leaf spring, and said middle piece of saidreleasing arm forming said shoulder member.

4. An overload tripping switch as set forth in claim 1, wherein saidmovable contact means is rotatably and displaceably supportedintermediate its ends by said rst link on a journal and is adapted to bedisplaced in a direction perpendicular to the lengthwise directionthereof, spring means disposed in said connection between said firstlink and said movable contact member urging said movable contact memberinto a direction away from said first link.

5. An overload tripping switch as set forth in claim 4, wherein saidjournal is carried by said first link and said spring comprises a coilspring, said coil spring encompassing said journal and having its freeend in engagement with said movable contact member on each side of saidjournal.

6. An overload tripping switch as set forth in claim 1,

wherein the connection of said releasing arm and said second linkcomprises a journal, said blocking member comprising a blocking armrotatably supported on `said journal and said shoulder member comprisessaid journal connecting said first link and said second link, springmeans associated with said blocking arm urging said arm into engagementwith said releasing arm, movement of said first link when said movablecontact member is in engaged position with said fixed contact beinglimited by the engagement of said blocking arm with said journalconnecting said first and second links.

7. An overload tripping switch as set forth in claim l, wherein eachside of said second link comprises a perpendicularly extending tab, saidhousing comprising a longitudinal cam terminating in a perpendicularlydisposed notch, said tabs being slidable along said cam and into saidnotch as said movable contact member is moved into engagement with saidfixed contact, the engagement of said tabs with said notch preventingmovement of the connected ends of said first and second links in adirection perpendicular of the longitudinal direction of said links bysaid connecting arm while permitting displacement of said links in saidlongitudinal direction.

8. An overload tripping switch as set forth in claim 7, wherein saidhousing comprises a pair of parallel plates and said cams compriseopenings in said plates, said second link comprising a pair of spacedparallel members disposed between said plates and each having a tabextending perpendicularly outwardly therefrom through said openings andinto engagement with said cam surfaces.

9. An overload tripping switch as set forth in claim l, wherein movementof said releasing arm to releasing position is controlled by a blockingarm, said heat sensitive member comprising first switch temperatureresponsive means associated with said blocking arm releasing saidblocking arm from blocking relationship with said releasing arm inresponse to predetermined movement of said first temperature responsivemeans resulting from an increase in switch temperature, and secondtemperature responsive means associated with said first temperatureresponsive means regulating said predetermined movement thereof inresponse to changes in the ambient air temperature.

10. An overload tripping switch as set forth in claim 4, wherein saidspring means disposed in said connection between said first link andsaid movable contact member comprises a leaf spring.

References Cited in the file of this patent UNITED STATES PATENTS(Addition to No. 806,157)

